Lubricating greases



Patented June 29, 1937 UNITED STATES PATENT OFFICE 2,085,533 LUBRICATINGGREASES Edwin N. Klemgard, Martinez, Calif., assignor to ShellDevelopment Company, San Francisco, Calif., a corporation of Delaware NoDrawing. Application May 5, 1934, Serial No. 724,220

11 Claims.

This invention relates to the preparation of rubber latex it waspossible to obtain a product of great stability, a very tenacioustexture, and excellent qualities of adhesion to metallic surfaces, whichproduct was therefore particularly lO adapted for use in conjunctionwith bearings carrying heavy loads or subjected to repeated shocks.

The present practice in the commercial manufacture of consistentlubricating greases is to produce various homogeneous mixtures andcombinations of sodium, calcium, aluminum, zinc, or lead salts of thefatty acids with hydrocarbon oils. One of the greatest troublesattendant on mixtures so produced is their unstable character and thetendency of the metallic soap and oil components to separate,

I have found that the addition of small amounts of rubber latex tends,in all cases, to retard this deterioration of greases very greatly, andusually to stop it entirely. It must be especially pointed out here thatthe addition to greases of rubber latex, which is a milky liouidconsisting of very minute rubber globules d spersed in a watery fluid,leads to entirely different effects from those obtained if ordinarycured or vulcanized rubber is dissolved in oil. as has been sometimesproposed in the prior art. The latex contains, besides water and rubber,minute but 5 effective quantities of various constituents such asproteins and resinous materials, as well as anti-coagulants such asammonia. These constituents are usually driven off and lost in theprocess of curing or vulcanizing the rubber, and

40 the incorporation of solid redissolved rubber into the grease ispractically ineffective, especially as it is difficult to obtain in thatcase a homogeneous mixing of the rubber with the grease, despite theinvolved and cumbersome methods used to that purpose. Latex containingfrom 30 to by weight of rubber hydrocarbons is preferably used in thisinvention, although stronger or weaker natural aqueous dispersions ofrubber may be employed.

In my application, Serial No. 471,428, I disclosed a process ofproducing improved lubricating greases by adding thereto small amountsof rubber latex and heating the mixture with a suitable agitation to atemperature sufficient to dehydrate the latex, whereby a product oftransparent homogeneous texture is obtained.

I have now discovered that it is not necessary to effect the dehydrationof the latex after it had been added to the grease, since the latexitself is added in relatively small quantities and the amount of waterit contains does not effect unfavorably the lubricating properties ofthe grease,

but on the contrary serves to improve them.

In carrying out my invention, I prefer to use a naphthenic base pale oilof about 300 seconds Saybolt viscosity at 100 F., although other viscousmineral oils, parafiinic as well as naphthenic may be used. This oil ismixed with a metallic soap of a fatty acid; calcium, sodium, aluminum,zinc and lead salts of any fatty acids of vegetable or animal origin,such as stearates, palmitates, oleates, etc., may be used. for thatpurpose. Some glycerine derived from the fatty materials may also beadded. The mixing may be effected by any accept-ed conventional method:for example, for the preparation of soda and lime base greases,reference may be had to my book on Lubricating Greases (The ChemicalCatalog Co.,

.Inc.). It may, however, be briefly remarked here,

that when preparing soda and lime base greases, the soap in the form ofa concentrated material, is placed at the beginning of the process in acompounding kettle, which may be of the steam jacketed type, and may beprovided with means for mechanical agitation, the oil being thereafteradded to the soap. When aluminum base greases are prepared, it ispreferable to place first the oil in the mixing kettle, and to add thealuminum soap of a fatty acid afterwards. The mixture of oil and soap isheated with agitation to about 250 F., when naphthenic base oils areused, in order to dissolve the soap and obtain a satisfac tory yield ofa transparent homogeneous material. If, however, the percentage of themetallic soap is above about 15%, or if an oil of the paraffinic base isused, a treating temperature up to about 350 F. may be necessary. When asatisfactory homogeneous material is obtained, further heating isdiscontinued and the emulsion is cooled to a suitably low temperature,such, for example, as about 200 F., so that substantially no evaporationof water from latex will take place upon its addition. Rubber latex isthen added and owing to its structure and character described above, itis readily incorporated in the emulsion by mechanical agitation. Afterthe rubber latex has been thoroughly dissolved in the grease, the massis further cooled, either before or after being discharged from themixer.

Depending on the kind of greases which it isdesired to manufacture, theamounts of the ingradients used in my process may vary betweencomparatively wide limits, starting with less than about 1% of metallicsoap and about 0.1% of rubber latex and ending with about of alkali ormetallic soap and 6% of rubber latex for very dense greases. Inallcases, however, the product obtained is a lubricating grease ofsemi-solid consistency, containing as its three essential ingredients amineral oil, a metallic alkali soap of a fatty acid, and non-dehydratedrubber latex.

I have found that through the addition of the latter substance a verystable gel structure is formed that is very resistant to separationusually caused by mechanical working or agitation. The stability of theproduct makes it eminently suitable as lubricant for gears, wheels, ballroller bearings and shackle bolts. The superiority of the greasescompounded according to my invention over the products heretoforeavailable on the market may be easily demonstrated by a number of tests.For example, in making 'stability tests, I experimented extensively withgreases of the following composition.

Example I Mixture A B Percent 300 pale oil 90. 5 90. 0 Percent aluminumsteerate 9. 5 9. 5 Percent rubber latex 0 0. 5

v Example II Mixture A B Tallow 5. 9 5. 9 Caustic soda. 0. 9 0. 9California red oil (1000 S. V. vis. F.) l2. 3 12. 3 Calif. bright stockS. V. vis. 210 F.) 19. 5 19.5 Mid-Continent steam refined cylinder stock61. 4 6i. 3 Rubber lat 0 0. 3

The .grease containing the rubber latex was found in both examples to beconsiderably more stable under all conditions. Both Mixtures A and Bwere subjected to prolonged mechanical agitation after whichthey werevery carefully examined with the following results: Mixture A showedpositive separation and signs of breaking down, while the texture ofMixture B was practically unchanged. After continuous standing for aconsiderable period of time without agitation, a sample of the greasecontaining rubber latex showed no oil separation, while free oil wasquite perceptible in the sample containing no rubber latex.

I claim as my invention:

1. In the process of manufacturing lubricating grease, the steps ofmixing a hydrocarbon oil with a metallic soap of a fatty acid derivedfrom vegthe consistency of a 6.0% of rubber latex.

3. In the process of manufacturing lubricating grease, the steps ofmixing a mineral oil with less than 15% of a metallic soap of a fattyacid derived from vegetable oils or fats, heating the mixture withsuitable agitation to a temperature between 150 and 250 F., to formgrease, cooling the grease to a temperature below 200 F., andincorporating with said cooled grease lessthan 6% of non-dehydratedrubber latex.

4. A lubricating grease comprising a hydrocarbonoil, a metallic soap ofa fatty acid derived from. vegetable oils or fats in a quantitysufiicient to give the compound the consistency of a grease, and a smallquantity of a non-dehydrated rubber latex. I

5. The composition of claim 4, containing less than about 60% metallicsoap of a fatty acid derived from vegetable oils-or fats and less thanabout 5% non-dehydrated rubber latex.

6. The composition of claim 4, containing less than about 15% metallicsoap of a fatty acid derived from vegetable oils or fats and less than5% non-dehydrated rubber latex.

7. The composition of claim 4, containing less than about 15% aluminumsoap of a fatty acid derived fromvegetable oils or fats and less thanabout 0.5% non-dehydrated rubber latex.

8. A lubricating grease comprising a hydrocarbon oil, a quantity ofmetallic soap obtained by saponifying a soap-forming material, saidquantity being suflicient to give the compound grease, and a smallquantity of a non-dehydrated rubber latex.

9.-A lubricating grease comprising a hydrocarbon oil, a small quantityof glycerine, a quantity of metallic soap obtained by saponifying asoap-forming material, said quantity being sufflcient to give thecompound the consistency of a grease, and a small quantity of anon-dehydrated rubber latex.

10. A lubricating grease comprising a viscous hydrocarbon oil, ametallic soap of a soap-forming acid in a quantity sumcien't to give thecompound the consistency of a grease, and'a small quantity of anon-dehydrated rubber latex.

11. A lubricating grease comprising a hydroby saponifying a fattymaterial, said being sufficient to give the compound the consistency ofa grease, and a small quantity of a non-dehydrated rubber latexcomprising rubber and water in a ratio substantially corresponding tothat of a natural latex.

EDWDI N. miEMGARD.

